Sulphauro compounds and processes for their production



Patented F eb. 27, 1945 SULPI-lAURO COMPOUNDS AND PROCESSES FOR THEIR PRODUCTION Nelson R. Trenner, We'stfield, and Frederick A.

Bacher, Garwood, N. J., assignors to Merck & 00., Inc.,- Rahway, N. J., a corporation of New Jersey No Drawing." Original application December 13,

1941, Serial No. 422,924.

Divided and this application May 10, 1944, Serial No. 534,992

2 Claims. (01. 260-430) succinic acid in 1270 cc. of water is added to the suspension. The mixture isheated on a steam bath until practically all the solid material is dissolved. 'The heating time should not exceed 30 minutes if aurous cyanide of the proper activity is used. The reaction should be carried out in a good hood because large amounts of hydrogen According to our invention, aurous cyanide or its auro-cyanide complex ion, such as a cyanaurite of the -formu1a MAu(CN)z, where M is an alkali metal, is reacted with organic mercapto compounds.

Fundamentally, the reaction of our invention may be illustrated by the following equation:

R-SH-FAu+- RSA11+H+ cetyl .mer-

reactions such as occur when auric chloride or aurous iodide "are used. Aurous iodide is especially unsatisfactory because it is intrinsically unstable, spontaneously decomposing into gold and free iodine. When aurous iodide is reacted with nercapto succinic acid, forexample, the iodine. attacks the acid and converts it to the disulphide with the result that considerable losses of gold occur and impuritiesfare introduced into the system which experience has shown are impossible to remove from the final product.

Furthermore, our process has the advantage EwampZe I One mol (223 gms.) of aurous cyanide is suspended in about 800 cc. of water.

A solution of 2.75 mols (415 gms.) of mercapto cyanide are evolved.

The solution is cooledto room temperature, filtered clear of any extraneous solids,'and evaporated to dryness on a steam bath. This step also should be carried out in a good hood because hydrogen cyanide is lost during the evaporation.

The solid residue is triturated with hot ethyl acetate (on a steam bath) using three or four portions. The residual solid is filtered off and washed with hot ethyl acetate. This treatment removes unreacted thiomalic acid which may be recovered from the ethyl acetate by simple evaporation. The filter cake of aurothiomalic acid is dried in vacuo at C. for several hours. The aurothiomalic acid thus prepared is analytically pure, is an almost white powder having no melting point, is freely soluble in water, and methanol, and its aqueous solution has a pH of about 3.2.

The reaction may be illustrated as follows:

COOH COOH 1 Hi 1 HI I a AuCN' HON HSH HSALI OOH UOOH Analysis of the aurothiomalic acid thus obtained:

A solution of 28.4 gins. of gold' chloride acid yellow Merck in 100 cc. of water is added slowly to a solution of 0.07 mol of sodium bisulphite, 0.275 mol of potassium hydroxide and 0.138 mol of potassium cyanide in about cc. of water. The mixture is heated at 100 C. for a short time. Any extraneous solids are filtered oii and the cold filtrate is added to a solution of 10.9 gms. of cysteine hydrochloride in about 80 cc. of 2.5 NHCl. Hydrogen cyanide is removed from the reaction mixture by passing nitrogen through it. The white insoluble, analytically pure aurocysteine process for preparing aurous cyanide.

The cetyl auromercaptan so obtained does not redissolve in ethanol. It is insoluble in all the usual solvents, both hot and cold.

We have found that when aurous cyanide is used in;the reaction, there is considerable variation in the speed and ease of the reaction, depending upon the physical state of the aurous cyanide. Therefore, we have devised a special Certain commercial-grades of aurous cyanide also may be used in our process. However, if such a commercialgrade of aurous cyanide is used, it should be thoroughly tested for reactivity prior to use in the reaction.

Our improved process for the production of @aurouscyanide is illustrated in the following example.

NHa

Analysis of the aurocyste'ine this obtained;

.C r H) 1 All Found 1.93 62.43 Theory 11.35 1.91 62.41

Example HI About 6.7 isms. of aurous cyanide suspended in cc. of water-isadded'to '10 ms. (100% excess) of p-acetaminoth'iophenol (p-mercapto-acetam ilide), prepared by the method of Zincke &'"J6rg (Ber. 42, 3362-1908) and Hinsberg (Ber. 39, 2429-1906). p-sulphauro-acetanilide separates. It is insoluble in water and acetone, gradually decomposes when heated but does not melt.

This reaction may be illustrated as follows:

v NHC'O'CH: NHc'o'cHi AE C HON I M SAu' Analysis of the p sulphauro-acetanilide thus obtained:

Au o H Found -i 54.9 26.43 2.29 Theory 54.26 e a/ 4 21 Aurothio acids such as aurcthiomalic acid, for

example, may beconverted to salts by treating with an appropriate base as, for example, calcium hydroxide. Example IV A alcoholic solution of cetyl mercaptan is treated with 50% of the theoretical -amount of Example V A solution of one mol (394 gms.) of reagent gold chloride, AuCh-HCL3H2O, in one liter of water is poured slowly and with stirring into a solution prepared by dissolving 4 mols (168 gms. 95% NaOH) sodium hydroxide, one mol -(110 gms. 95% NaI-ISOa) soduim bisul-phite, and 2 mols (103 gms. 95% NaCN) sodium cyanide, in the order given, in 2.5 liters of water. A white precipitate is formed, which dissolves on heating. The mixture isheated on a steam bath for about hour. Then, in a good hood, an equal volume (3.5 liters) of concentrated hydrochloric acid is added. Heating is continued in an open dish in the hood for one'hour, with frequent stirring. The yellow precipitate of aurous cyanide active aurous cyanide and the suspension refluxed untila large fraction .of the solid has disappeared. Hydrogen cyanide is evolved slowly during this process. I. The solids are .fllteredofi .from the hot solution, and the filtrate evaporated on the steam bath. A light yell'ow, amorphous residue is-.ob--

tained.

is collected on a glass filter and rinsed with water.

The aurous cyanide is washed by suspension in approximately 10 liters of .water, :and filtered.

This is repeated at least once after the filtrate is found to be free from chloride by testing with .silver nitrate. Yield of aurous cyanide,

The aurous cyanide should be kept moist and in the dark until it is used.

Modifications maybe made in carrying'out the present invention without departing from the spirit and scope thereof anjd'we' are to be limited only by the appended claims.

1."The process comprisin r ti g a mercapto compound of the lformula WhereR is an aryl radical, with .a substance selected from the group consisting .of aurous cyanide and alkali aurocyan'ides, to iform the correspondingauro .thio compound.

.2. The process comprising reacting p-mercap- .toacetanilide a substance Selected from the .group consisting of aurous cyanide and alkali aur,ocyanldes.

R. TRENNER. EREDERIQ .A. BACHER. 

